Gas operated gun mechanism

ABSTRACT

In a paintball gun mechanism compressed air is admitted through passages ( 16 ) to the interior of the barrel ( 10 ) where it will move forward a hollow bolt ( 11 ) until it can escape through the bolt ( 11 ) to fire a paintball. The bolt ( 11 ) is then moved backward by compressed air in a chamber ( 15 ) until a central formation ( 12 ) of the bolt ( 11 ) enters a guide ( 13 ) to close a firing chamber ( 14 ) behind the bolt ( 11 ). The invention provides a valve member ( 17 ) independent of the bolt ( 11 ) which is biased by a spring ( 18 ) to close off the firing chamber ( 14 ) from the passages ( 16 ) except when displaced by the formation ( 12 ) of the bolt ( 11 ) during a final part of the rearward movement of the bolt ( 11 ).

This invention relates to an improved gas operated gun mechanism and particularly but not exclusively to an improved mechanism for a paintball gun. Paintball guns are used in paintball war games in which the participants fire paintballs at one another to mark a “hit”.

A paintball gun mechanism is known in which compressed air in a canister connected to the gun housing is communicated with the interior of the barrel of the gun to expel a paintball therefrom through a bolt which moves forward in the barrel to open the communication, when the trigger of the gun is pulled, and backward to close it. This means that for the whole time that the bolt is not in the closed position air is escaping even after a paintball has been fired, which represents a considerable wastage of compressed air. Moreover the bolt moves to its closed position against the pressurised air behind it, requiring considerable force to move the bolt.

In an effort to solve this problem it has been proposed to attach to the rear of the bolt a tail having an enlargement which will fill an orifice in the path of the compressed air between the canister and a firing chamber in the barrel behind the bolt when the bolt is in its open position, thereby cutting off communication between the canister and the firing chamber as a paintball is fired. This solution, however, is far from perfect. As soon as the bolt begins to move toward its closed position communication with the canister is again opened so that some wastage will occur before the bolt is fully closed. The bolt will still be working against compressed air behind it as it moves to its closed position. Even more seriously, the length of the tail must be at least equal to the travel of the bolt, requiring an extension of the rear of the gun housing which will make the gun unduly large and unweildy.

A principal object of the present invention is to resolve these problems by replacing the tail and its enlargement with a valve member which is independent of the bolt and which is moved to an open position only during a final part of the movement of the bolt to its closed position. As soon as the bolt begins to move forward the valve closes so that during the greater part of the movement of the bolt from its open to its closed position no compressed air is admitted to the firing chamber to resist the movement of the bolt. Movement of the valve member is so small that it requires no extension of the gun housing to accommodate it.

In accordance with the present invention there is provided a gas-operated gun mechanism of the kind in which a bolt is reciprocable in a barrel between positions opening and closing communication between a source of compressed gas behind the bolt and the interior of the barrel forward of the bolt, thereby in said open position expelling a projectile from the barrel, communication between the source and the rear of the bolt being through a firing chamber of the barrel behind the bolt, characterised in that between said source and the rear of the bolt and not connected to the latter a valve is provided which is biased to a closed position in which it closes communication between said source and the firing chamber but which is displaced by the bolt to an open position during a final part of the movement of the bolt to the closed position of the latter, thereby re-charging the firing chamber.

Preferably the valve is spring biased to its closed position.

The bolt may be tubular with a coaxial formation which enters a guide within the barrel when the bolt is retracted, said formation leaving the guide as the bolt reaches a forward, firing position thereby allowing compressed gas from the firing chamber to flow through the bolt.

In a preferred embodiment of the invention the bolt is moved forward to its firing position by compressed gas from the firing chamber and is retracted from its firing position by the admission of compressed gas to an annular chamber between the bolt periphery and the barrel.

A preferred embodiment of the invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which:

FIG. 1 is a sectional elevation of the mechanism of a paintball gun in accordance with the invention, and

FIG. 2 is a similar view of the mechanism of FIG. 1 but with the bolt in the firing position.

The barrel 10 of a paintball gun contains a tubular bolt 11 having a coaxial central formation 12. The formation 12 is reciprocable into and out of a tubular guide 13 fixed coaxially within the barrel 10 when the bolt 11 as a whole reciprocates in the barrel. To the rear of the guide 13 is a firing chamber 14 within the barrel. When the bolt 11 moves backward from the position of FIG. 1 to the position of FIG. 2 under the influence of compressed air introduced into an annular chamber 15 around the bolt compressed air is admitted to the firing chamber 14 from a canister (not shown) through radial passages 16. A latch (not shown) holds the bolt in its retracted position. When the trigger (not shown) of the gun is pulled the latch is released and the chamber 15 evacuated so that compressed air in the firing chamber 14 can push the bolt 11 forward from the position of FIG. 2 to the position of FIG. 1 until the formation 12 emerges from the guide 13 so that compressed air can flow through the bolt and expel from the barrel 10 a paintball (not shown) in front of the bolt. The way in which a paintball is selected from a magazine to lie in front of the bolt 11 when the latter is retracted is well known per se and will not be described.

In accordance with the present invention an elongated valve member 17 is provided which is urged by a compression spring 18 to the closed position of FIG. 1 in which it shuts off communication between the air passages 16 and the firing chamber 14. During a final part of the rearward movement of the bolt 11 from the firing position of FIG. 2 to the retracted position of FIG. 1 the rear end of the formation 12 strikes the leading end of the valve member 17 and displaces the valve member to the open position of FIG. 1 so that the firing chamber 14 is recharged with compressed air.

By this arrangement, when the bolt is in the firing position of FIG. 2 compressed air is exhausted from the firing chamber 14 and therefore the bolt 11 is not working against compressed air when it is retracted by pressure in the chamber 15. The travel of the valve member 17 is so small that the housing of the gun requires very little enlargement to accommodate it. 

1. A gas-operated gun mechanism comprising a bolt which is reciprocable in a barrel between positions opening and closing communication between a source of compressed gas behind the bolt and an interior of the barrel forward of the bolt, thereby in said open position being adapted to expel a paintball from the barrel, communication between the source and the rear of the bolt being through a firing chamber of the barrel behind the bolt, wherein between said source and the rear of the bolt and not connected to the bolt a valve is provided which is biased to a closed position in which it closes communication between said source and the firing chamber but which is displaced by the bolt to an open position during a final part of a movement of the bolt to a closed position of the bolt, thereby re-charging the firing chamber.
 2. A gas-operated gun mechanism as claimed in claim 1, wherein the valve is spring biased to the closed position.
 3. A gas-operated gun mechanism as claimed in claim 1, wherein the bolt is tubular with a coaxial formation which enters a guide within the barrel when the bolt is retracted, said formation leaving the guide as the bolt reaches a forward, firing position thereby allowing compressed gas from the firing chamber to flow through the bolt.
 4. A gas-operated gun mechanism as claimed in claim 1, wherein the bolt is moved forward to firing position by compressed gas from the firing chamber and is retracted from the firing position by admission of compressed gas to an annular chamber between the a periphery of the bolt and the barrel.
 5. A mechanism for a gas-operated gun having a barrel from which a projectile is fireable, the mechanism comprising: a bolt; a sleeve fixedly locatable in the barrel; a valve assembly; and and a chamber located between the sleeve and the valve assembly, wherein: (a) the bolt is reciprocable within the sleeve between a forward firing position and a retracted position, (b) the valve is actuatable to permit communication between a gas source and the chamber when the bolt is in the retracted position but closed to prevent said communication as the bolt moves to the firing position, (c) and the bolt allows secondary communication between the chamber and the barrel, via the sleeve, as the bolt moves to the forward firing position, to fire the projectile located in the barrel of the gun.
 6. A mechanism according to claim 5, wherein the valve assembly comprises a forward end which is reciprocable within the sleeve when the bolt alternates between the forward and retracted positions.
 7. A mechanism according to claim 5, wherein the valve assembly is spring biased to a closed position. 